A look at the top Senate races

WASHINGTON — Democrats narrowly control the Senate — 51-47 with two independents who caucus with the Democrats — and Republicans are upbeat about their chances of seizing control in November. Here's a look at the top races.

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The Senate's two most senior Republicans — Indiana's Dick Lugar and Utah's Orrin Hatch — are facing the toughest races of their long careers.

Hatch must survive a GOP state convention on April 21 that was the undoing of Republican Bob Bennett in 2010. Tea partyers knocked out Bennett at the convention dominated by hard-core GOPers, and they've targeted Hatch, who voted for the Wall Street bailout in 2008 and has been in the Senate since 1977.

The convention requires a candidate to get 60 percent of the vote. If not, the first two finishers move on to a primary.

"It's ready made for activists to dominate the process," said Matt Kibbe, president and CEO of FreedomWorks, a national group that helps organize tea party activists. "This time the difference is Hatch knows it's coming. I think we'll beat him. It's the most likely success of our top four targets."

Conservative activists are looking to state Sen. Dan Liljenquist, among the possible alternatives.

Lugar is under siege from FreedomWorks, the anti-tax Club for Growth and the Tea Party Express, who complain about his vote to raise the nation's borrowing authority and projects for Indiana. But Lugar's toughest problem now is his home — he's lived in northern Virginia since 1977. State officials say it's legal, but he's been pummeled for using the address of an Indianapolis home he sold in 1977 for his driver's license and voter registration.

In a clear sign of nervousness, Lugar spent some of his $4 million from his campaign account on an ad that criticized his tea party-backed rival, state treasurer Richard Mourdock, for "mudslinging." The ad airing this week says "Mourdock and his D.C. cronies are attacking Senator Lugar again."

No matter what the outcome in Utah, Republicans are expected to hold the seat. A Lugar loss in the May 8 primary would put Indiana in the mix, with Democratic Rep. Joe Donnelly looking to capture the Senate seat in a state that narrowly went for President Barack Obama in 2008.

MARQUEE MATCHUPS

If Republicans can hold Massachusetts and Nevada, win one or two of the open seats and knock off a Democrat or two, they can claim the Senate. If Democrats unseat Massachusetts' Scott Brown and Nevada's Dean Heller, they have a solid chance of keeping their majority

Brown stunned Washington, Massachusetts and the rest of the political world early in 2010 when he won a special election and captured the seat held by the late Sen. Ted Kennedy. Democrats got their top recruit, consumer advocate Elizabeth Warren, one of a record 11 Democratic women running for Senate seats this year.

Brown has $12.9 million cash on hand, according to the FEC reports as of December. Warren has $6.1 million for what is certain to be a fierce fight for the critical independent vote. Both candidates have pledged to keep out outside groups.

In Nevada, Republican Dean Heller replaced former Sen. John Ensign, who resigned after an extramarital affair with his aide's wife and a Senate ethics investigation. Challenging Heller is House Rep. Shelley Berkley, who has the backing of Senate Majority Leader Harry Reid. The two have just under $4 million each for a hard-fought contest that pits Heller, from the rural northwest, against Berkley, well-known in the southern part of the state and heavily populated Las Vegas.

DEMOCRATS IN GOP CROSSHAIRS

Missouri Sen. Clare McCaskill and Montana Sen. Jon Tester, who won in the 2006 midterms, are hoping the higher turnout of a presidential election year works to their benefit in states that went for Republican presidential nominee John McCain in 2008. The two are top Republican targets and have already faced an onslaught of ads from Republican-allied groups.

Tester is facing Denny Rehberg, the state's lone representative. McCaskill's rival will be decided in the Aug. 7 primary involving Rep. Todd Akin, former state treasurer Sarah Steelman and St. Louis businessman John Brunner.

The GOP is trying to portray Rep. Tammy Baldwin as too liberal for Wisconsin's open seat. The state's Republican voters will choose on Aug. 14 among three candidates — former Gov. Tommy Thompson, who last ran for governor in 1998, former Rep. Mark Neumann and state Assembly Speaker Jeff Fitzgerald.

Virginia pits former Gov. Tim Kaine against former Sen. George Allen in a race for an open seat. Obama's performance in the state that he won narrowly in 2008 will influence the Senate outcome.

When Democratic Sen. Kent Conrad announced he would not seek another term, Republicans and some Democrats immediately put North Dakota in the GOP column. But former attorney general Heidi Heitkamp's criticism of extreme Washington politicians has resonated in the state. Her rival is Rep. Rick Berg, the state's lone congressman.

The burning question is whether the Republican-leaning state — it went heavily for George W. Bush in 2004 and McCain in 2008 — would elect a non-incumbent Democrat for Senate.

The flip side of North Dakota is Hawaii, where Obama is hugely popular in his native state. Republicans are hoping former Gov. Linda Lingle will benefit from ticket splitting. Democrats decide on Aug. 11 between former Rep. Ed Case and current Rep. Mazie Hirono.